Among semiconductor devices, diodes are required to have high withstand voltage, small reverse saturation current, and the like. Silicon carbide (SiC) used as a semiconductor material has a width of a forbidden band of 3 eV or more, excellent controllability of electric conductivity at high temperature, and a dielectric breakdown electric field that is about an order of magnitude higher than that of silicon. Therefore, silicon carbide is expected to be applied to a diode in which reverse saturation current is small and withstand voltage is high. For example, a Schottky barrier diode in which silicon carbide is used and reverse leakage current is reduced is known (Patent Document 1).
However, in the case of using silicon carbide, it is difficult to obtain crystals with good quality, and further, there is a problem in that a process temperature for manufacturing a device is high. For example, an ion implantation method is used to form an impurity region in silicon carbide; in that case, heat treatment at 1500° C. or higher is necessary in order to activate a dopant or repair crystal defects caused by ion implantation.
In addition, since carbon is contained as a component in silicon carbide, an insulating layer with good quality cannot be formed by thermal oxidation. Furthermore, silicon carbide is chemically very stable and is not easily etched by normal wet etching.